قَالَ: ثُمَّ انْطَلَقَ فَلَبِثْتُ مَلِيًّا، ثُمَّ قَالَ لِي: يَا عُمَرُ! أَتَدْرِي مَنِ السَّائِلُ؟ قُلْتُ: اللَّهُ وَرَسُولُهُ أَعْلَمُ. قَالَ: فَإِنَّهُ جِبْرِيلُ أَتَاكُمْ يُعَلِّمُكُمْ دِينَكُمْ
Translation: The visitor departed, and after some time the Prophet ﷺ asked ʿUmar if he knew who had questioned him. ʿUmar said: Allah and His Messenger know best. He replied: It was Jibril; he came to teach you your religion.
The visitor left. After some time, the Prophet ﷺ asked ʿUmar whether he knew the questioner. ʿUmar replied that Allah and His Messenger knew best. The Prophet ﷺ disclosed that the visitor was Jibril, who had come to teach them their religion.
فَلَبِثْتُ مَلِيًّا indicates that some time passed. أَتَدْرِي means “Do you know?”, and يُعَلِّمُكُمْ دِينَكُمْ means “He was teaching you your religion.”
This closing statement reveals the instructional purpose behind all the earlier questions.
Source: Muslim